1. Field of the Invention
The invention pertains to planetary gear assemblies used to improve the torque/speed characteristics of the drive motors of power tools.
2. Description of the Prior Art
Various types of power tools such as drills, impact wrenches and the like utilize electric motors. Planetary gear train assemblies are commonly used with the drive motor to gear down the speed of rotation of the output shaft and to increase the torque transmitted from the drive motor. Such planetary gear trains are commonly multi-part assemblies, including a ring gear, the output shaft, planet gears, a planet gear carrier and means interconnecting the output shaft and the gear carrier. These parts are of complicated construction and, while it is known to provide a plastic ring gear, the other parts are all typically machined metal parts which are very expensive to manufacture. Also, the large number of parts tends to make assembly complicated and expensive.
It is known to provide the output shaft and the planet gear carrier as one piece, such an arrangement being disclosed in U.S. Pat. No. 4,983,152. But the carrier frame/shaft unit is still formed entirely of metal and is very expensive to manufacture.
Also, in prior power tools, it has been difficult to properly align the drive train accurately in the tool housing, while at the same time providing an economical assembly.